First report of Rhodnius montenegrensis (Hemiptera: Reduviidae: Triatominae) in Bolivia

ABSTRACT Background: The subfamily Triatominae, which comprises 157 species, carries the protozoan Trypanosoma cruzi, the etiological agent of Chagas disease. This short communication reports for the first time the occurrence of Rhodnius montenegrensis in Bolivia. Methods: Active searches were carried out on palm trees of the genus Oenocarpus in Beni district, Bolivia. Results: Fifteen R. montenegrensis specimens were collected from a rural area of the Beni district, Bolivia, and tested positive for T. cruzi. Conclusions: This new report expands the geographic distribution of the species in Latin America. Due to their ability to transmit trypanosomatids, the species deserves the attention of vector control programs.

The subfamily Triatominae is currently composed of 157 species with 18 genera [1][2][3]   being palm trees of the genus Attalea. However, they have been reported to be present in and around homes (intradomiciliary and peridomiciliary), posing an epidemiological risk of transmission of Chagas disease, since they act as significant transmitters of natural infection with Trypanosoma cruzi (Chagas, 1909) (Kinetoplastida: Trypanosomatidae) 7-8 .
The species Rhodnius montenegrensis has been registered only in Brazil, occurring in the states of Acre 9 , Amazonas 10 , Rondônia 11 , and Roraima 12 . This distribution has been expanded with the present study, which aims to describe the first report of the occurrence of R. montenegrensis in Bolivia. Between 2019 and 2020, 15 specimens of R. montenegrensis were collected from rural areas in the municipality of Guayaramerin, Beni, and Bolivia (Figure 1).
Guajará-Mirim, in Brazil, borders Guayaramerin, located in Bolivia, and is considered a twin city separated by the Mamoré River 13 . The first record of the species R. montenegrensis in 2012 was made in the municipality of Monte Negro 11 , Rondônia, a city close to Guajará-Mirim; thus, we may justify the presence of this specimen in Bolivia due to the surroundings of these municipalities.
The specimens were collected by means of an active search in palm trees (genus Oenocarpus) distributed in areas of secondary forests and pasture lands. Using tweezers and machetes to assist in thinning, the bracts were removed (as they can lodge a large number of invertebrates and small vertebrates), and the triatomines were collected one at a time to avoid damage. We captured 15 triatomines -nine adults, three fourth-instar nymphs, and three fifth-instar nymphs of R. montenegrensis.
For identification, we used the method described by Rosa et al. (2012) 11 . Fifteen triatomines were subjected to infection analysis and identification at the Parasitology Laboratory of the Department of Biological Sciences, Faculty of Pharmaceutical Sciences, Universidade Estadual Paulista, Campus de Araraquara. The specimens were added to the Triatominae collection MA, USA), using the digestive tract of each collected triatomine suspended in absolute alcohol and stored at -20°C. For the PCR, we followed the kDNA-PCR protocol described by Márquez et al. (2016) 14 . Among the 15 samples tested, 6 yielded positive results for T. cruzi (Figure 3).
Rhodnius montenegrensis and R. robustus present some morphological similarities; however, morphological 15 , morphometric 15 , transcriptomic 15 , and cytogenetic 16 studies have allowed differentiation of the species and confirmed the specific status of R. montenegrensis. For this reason, there may be an erroneous description of the distribution of R. montenegrensis, both in Brazil and in other Latin American countries (with an emphasis on countries bordering Brazil).
R. montenegrensis specimens collected from palm trees and residences revealed their ability to adapt to the human environment, dispersal, and mobility 17 . Studies conducted in Acre, Amazonas, and Rondônia demonstrate the predominance of this species in its natural ecotope, and intrusion into residences and the infection rate for T. cruzi in this species are significant in the localities where they were captured [9][10][11]17 . Another aspect described in these studies is the non-occurrence of domiciliation of R. montenegrensis 10,17 .
With the expansion of this species in Brazilian states and a neighboring country, such as Bolivia, it is pertinent to affirm the epidemiological importance of including this species in the transmission cycle of Chagas disease in the Brazilian and international Amazon.
Rhodnius montenegrensis has also been reported in domestic environments, but only in the countryside 18 . In addition, it has been found to be naturally infected with Trypanosoma rangeli Tejera, 1920, which is of major importance because the difficulty in isolation and diagnosis may be related to a double trypanosomatid infection, which can lead to false positive or true positive results for Chagas disease 18,19 . This new report on the occurrence of R. montenegrensis expands the geographic distribution of the species in Latin America, with Bolivia being the second country to register the presence of the insect and increasing the number of species described in the locality.